Attrition mill



G. F. AlNsA ATTRITION MILL Sept. 5, 1939.

Filed 0-Ct. 4 1933 2 Sheets-Sheet 1 wgNEx 1 trifugal force and'causing a massof agglomerate' Patented Sept. 5, 1939 PATENT OFFICE ATI'BJTION MILL George Foye Ainsa, San Francisco, Calif., assignor of one-third to Dolores Ainsa, Calif .Application October 4,

I `2'Ciaims. The present invention relates generally to an attrition mill of the type in which an agglomerate of loose and lumpy material is reduced or pulverized by'a rubbing action between the particles thereof, and more particularly to animproved form of mill wherein, in'addition to' the rubbing action between the particles, there is provided means for projecting the particles by centrifugal force against astationary or rotating anvil to thus effect a reduction of the agglomerate by a combined rubbing and impact operation.

An object of the present invention is to provide an attrition mill for reducing and pulverizing an agglomerate which operates on a combined rubbing and impact principle to reduce .the agglomerate to powdered form. y

' Another object of the present invention is to provide an attrition mill wherein the larger particles of the agglomerate will be reduced and disintegrated in a continuous manner by interimpaction created-by centrifugal force.

Another object of the' present inventionis to provide in an attrition mill ofthe above character means for returning the unreducedl particles of the agglomerate to the reducing elements of the mill and separating the ilner particles therefrom by a process of flotation.

' In the art to which the presenty invention re` lates there has been devised a large number of mills for reducing ores and'other agglomerate by retaining portions thereof in a receptacle by centhus held to rub .against a second stationary o'r relatively movable mass of the agglomei-ate.l For ,l illustrations of apparatus of this characterl reference may be had to United States Patent Number 429,679, lssued'June 10, 1890, to H. A. D uc, Jr., United States Patent Number 498,03'Lissued May 23, 189,3, to T.\L.Sturtevant,. and United d States APatent Number 1,8'77,517,-issued Septemvkber 13, 1932, to JH. Macartney. i y

In each of Athe mills illustrated in the above patents the agglomerate is reduced solely by a rubbing action which takes place between the force and. passes out of the mill' between grinding rings disposed about'the periphery of the centrifugallyA operating rotor elements. Mills of this' relatively movable particles of the agglomerateV as it travels under the iniluence of centrifugal Berkeley,

1933, Serial No. 692,073

(Cl. 83-46) an impact member, and against each other and thus reduced by a combined impact and rubbing action without subjecting the mass to an excessive pressure. v

In accordance with one form of the presentin;Z .5 vention the agglomerate is fed by gravity into a horizontally disposed rotating element and is thrown therefrom by centrifugal force against an impact ring or anvil, from which the heavier particlesV are directed back into the feed stream :if-.510

' the agglomerate, while the remaining unreduced portion thereofis returned to the hopper feed stream by otherimeans until the agglomerate is l reduced to the desired degree of flneness, after which the finely divided agglomerate is 'conductedw away from the mill by flotation or other means.

In another embodiment of the present invention the agglomerate is fed by gravity into one rotating element and thrown therefrom by centrifugall-force into a second and oppositely rotatingf 20 centrifugal rotor which will direct the larger particles back into the feed stream until the agglomerate is reduced to the desired degree of fineness and finally discharged from the mill.

For a lbetter understanding of the invention-85 and the mode of operation reference should be had to the accompanying drawings wherein there is shown, by way of ,illustration and not of limita- Otion, preferred embodiments thereof.

In the drawings wherein like numerals desig-l nate like parts throughout the several views,

. Figure 1 is a vertical sectional view of a mill constructed in accordance with one embodiment of the present invention,

Y Figure 2 'is a vertical sectional view takenalong' line II--II of Figure 1, looking in the direction of the arrow's',

Figure 3 is a fragmentary sectional view taken along line lIIj--lII of Figure 1, looking in the direction of the arrows, [Figurei is a vertical sectional view of a modiiied mill having two centrifugal agglomerate throwing elements. Figure 5 is a vertical sectional view taken along line V--V of Figure 4, looking in the direction ofl 45 the arrows, and

^Figure 61s a side view of a modiiled drum which may be substituted for the drums illustrated in the'other figures of the drawings, should it be desired to construct a mill for the reduction of 50 the agglomeratein dry form.

The yembodiments of the presenti invention illustrated in the drawings are particularly adapted to thereduction of loose and broken lumpy material,- such as ores, cement, rock, clay and the 55 per I4 may project.

like. As shown in Figures 1, 2 and 3 of the drawings, the mill has a base 'I0 that may be secured to a suitable foundation and support the several elements of the mill in cooperating relation. Mounted upon the base I there is provided a stationary pedestal II which supports a horizontally disposed centrifugal rotor I2 and at the other end of the base there is a movable pedestal I3 which supports a hopper I4 having a discharge spout I5, the latter of which is held in spaced relation with the rim of the centrifugal rotor I2. f

Disposed about the centrifugal rotor I2 andthe discharge spout I5 there is a rotatable drum I5l which forms an enclosing housing about the reducing elements of thegmill. The rotation of .the drum I6 is provided for by externally disposed annular rails I1 carried thereby which engage two pairs of spaced rollers I8 carried by parallel shafts I9. Within the rotatable drum IB there is a hardened steel anvil or impact ring which "is adapted. to cooperate with the centrifugal rotor I2. `The impact ring 2li` is of heavy construction and has a hemispherical interior surface. It is mounted in spaced relation with the walls yof the drum I6 by means of stays or struts 2l.

The centrifugal rotor I2 is mounted upon a horizontally disposed shaft 22 that carries a pulley 23 whichpis adapted to be connected with any suitable sourceI of power by means of a Ydriving belt 24. The rotatable drum I6 is also adapted to be driven from the same source of power through a worm 25, aV worm gear 26, and a pulley 21 whichis connected by a belt 28' with a larger pulley 29. The pulley 2S' is carried by a transversely disposed shaft having two beveled gears 3l which mesh with beveled gears 32 secured upon the shafts I9. Whenthe shaft 22 is driven by a suitable source of power the centrifugal rotor I2 willrevolve at a high speed and the drum I5 will be rotated' in the same or a reverse direction at a considerably slower speed. The centrifugal rotor I2 is preferably disposed with its open end in a` plane substantially midway between the ends of the drum I6 and therefore, one end of the drum is provided with a reentrant or inwardly projecting conical end wall 33 which terminates closely adjacent the outer periphery of the rotor. The other end of the drum I6 is provided with a straight end wall 34 having a central opening 35 through which the discharge spout I5 of the hop- When the above described mill is in operation -the particles .of the agglomerate will be swirled around into contact with each other and projected against the impact ring 20 until they have been reduced to the desired fineness. During this operation' the reduced and some of the unreduced particles of the-agglomerate will fall down into the bottom of the rotatable drum I6 where the particles, havingthe desired degree of lineness, will be decanted or floated out through the opening 35 andinto a discharge pipe 36 with the excess water 31 which will be introduced into the mill when it is in operation The heavier and unreduced particles of agglomerate will settle in the Water at the bottom of the drum I6 where they l'lliv will be picked'up by spirally disposed scoops or pockets 38which terminate against radial fins 39, and thus be directed back into the active or. reducing zone of the mill..

The agglomerate may be discharged from the hopper I4 and into the mill in either a wet or a If\-thev agglomerate is not sufwater and finished material from the drum I6 ablevdrum 53. This drum '53, like the drum I6 end of the drum 53.

water may be added through the hopper I4, Whereas, if it is desired to introduce the agglomerate into the mill in a dry condition the water, necessary to provide for a flow from the mill, as suggested above, may be added to the drum I6 5 through the opening 35 in the end Wall 34. Since the depth of the water in the drum I6 and the rate of flow therefrom will effect the fineness of the material decanted, the diameter of the o'pening 35 in the end wall 34 is so proportioned, with respect to the inside diameter of the drum I6, thatv the drum will hold a definite depth of water or other fluid 31 and therefore, with means for regulating the rate vof the water feed, the degree of fineness of the agglomerate decanted therefrom can be controlled.

The mill .illustrated in Figures 4. and 5 of the drawings is substantially similar in construction and mode of operation to the mill described above, except for the differences which will be hereinaftervpointed out. In the mill now to be described there is provided an inner centrifugal rotor 4ll which is adapted to be driven at a high rotative speed in one direction and a second or outer centrifugal rotor 4I which is adapted to be driven at a high rotative speed in an opposite direction. These' rotors are mounted upon suitable bearings carried by a pedestald 42 and are adapted to be driven by power transmitting belts 43 and 44 respectivelyt The belt 43 operates upon a pulley 45 carried by `a shaft 46 which supports the inner rotor 40, and the belt 44 engages a pulley 41 that is formed upon a rotatingsupport 48 which carriesthe outer rotor 4I. The pedestal 42 is secured at one end of a suitable foundation base 49 and at the other end of this base there is an adjustable pedestal 50 which supports a hopper 5I having a discharge pipe or chute 52. Surrounding the centrifugal rotor elements 40 and 4I there is a rotatpreviously described, is provided with externally disposed annular rails I1 which engage spaced rollers I8 to thus form a trunnion-like mounting therefor. In this embodiment the,spaced rollers I8 are keyed upon parallel shafts 54 that carry pulleys 55, over which a connecting belt 56 is placed.v In order to impart movement to the drum 53', one of the shafts 54 is provided with a pulley 51 havinga belt 58 that connects with ay suitable source of power.

As shown in the drawings, the end of the chute 52 is disposed in closely spaced relation with the rim of the inner centrifugal rotor 40 and projects through'the,outer'centrifugal rotor 4I 4so that when the agglomerate is thrown out by the inner rotor 40 and against -the outer rotor 4I it will f all or be thrown downwardly into the chute 52 where it will comingle with the agglomerate being fed to the mill. The unreduced agglomerate, which is not thus redeposited in the chute 52, will be picked up by a plurality of..inclined pockets or scoops 59 formed upon the interior of the drum 53. These scoops 59- are so shaped and inclined that the agglomerate picked up thereby, as the drum 53 rotates, will be carried substantially to the top of the drum andthen dropped clear of the rotor elements 4'0 and 4I and into the chute 52. While the .scoops 5 9 are thus operatingto return the unreduced agglomerate t'the chute 52, the finer particles of the agglomerate will be decanted or floated from the mill by the water 31 which will accumulate in the bottom lof the drum and spill out and into the discharge pipe 36 through a discharge opening 60 provided at the In the drawings the openings 35 and 60, in the drums IG and 53 respectively, are shown as having a flaring flange 5I which serves to direct the flow of water and finely reduced agglomerate into the discharge pipe 36. As an additional means for controlling the size ofthe agglomerate which may be carried or floated away from the mill with the excess water 31, there may be provided an annular screen 62 having any desired mesh. In the present invention advantage is taken of the well known fact that the neness of the agglomerate discharged by the flotation method, described above,.may be controlled by regulating the depth of the water at the bottom of the rotatable drums I6 and 53. Therefore, as stated above, the mill may be designed in this respect by' varying the 'inside diameter of the discharge opening 60 at' theend thereof to provide for a proper depth of iiuid'in the drum. If adjustability in these dimansions should be desired in a particular mill it cari be obtained by providing a plurality of end walls having discharge openings of different size. The same'result can also be accomplished by mounting a plurality of nesting rings in the discharge opening at the end ofthe mill to thus reduce'its diameter. i

Each of the centrifugal rotor elements I2 and 43, described above, is provided with a hardened steel ring 63 at its periphery which will Yreduce thepossibility of excessive wear at this point by the discharge of the agglomerate therefrom by In order to' prevent excessive wear at the end of the hopper dischargevspout I5, there is provided a hardened steel lip 6I which will cooperate with the ring 63 to'direct all but the finely reduced agglomerate into the centrifugal rotor I2. The

hopper discharge chute 52 of the mill shown in Figure 4 of the drawings is likewise reinforced by the provision of a hardened steel lip 65 which will cooperate in the above manner with the ring 63 at the discharge end of the'centrifugal rotorv Il).

A s an additional-adjunct, the mills illustrated in the drawingsareshown as having a source of 'water supply -QG with connections which will permit the Water to be introduced either in the hoppers Il and,5I or directly into the drums I6 and Il. g v f While the mills contemplated by this invention have beenV described above in a form which is particularly adapted to the reduction of wet agglomerate they are also suitable for the reduction of dry agglomerate. In this latter event, however,- thevreduced agglomerate can not be withdrawn from the mills by the flotation process described above and, therefore, other means for discharging the line agglomerate fromthe mills must be provided. I

In Figure of the drawings there is shown a rotatable drum 51 for a dry grinding'mill. 'As here illustrated, the vrotatable drum 51 is provided with screens 33 of proper mesh located between the scoops or pockets which are formed upon the inside of the drum, as is-the case with shroud over the drum 61 in order to collect the finely powdered agglomerate.

Before describing the operation of the mills illustrated in the drawings it should be stated that, as shown, the parts are assumed to be in 5 movement and that the centrifugally projected particles thrown out by the rotor elements have been omitted in order to fully disclose the details of the several parts of the -mills with which they contact. When the mills' are in'- operation these 10 omitted particles will be projected in the direction indicated by the dot and dash arrows that have been applied to the drawings. In other words,

"when the mills are in operation the hopper discharge spouts or feeding chutes will contain more agglomerate thanis illustrated. The upper limit of the agglomerate illustrated is intended to represent the slip surface between the moving particles of the agglomerate and a portion thereof which will feed more slowly at the bottom of the m spouts or chutes. The rotor elements are also shownas partially filled with agglomerate which will be retained by centrifugal force. The conical formation of the agglomerate represents the nominal slip line along which the excess agglomerate will be thrown out of the rotor elements by centrifugal force. y.

'I'he operation of the mill illustrated in Figure 1 of the drawings may be described as follows:

When the rotor I2 is driven at a high rotative I speed and the agglomerate is fed thereto by means of the hopper discharge spout I5, the agglomerate picked up by the rotor I2 will be thrown outwardly at a high velocity by centrifugal force and against the impact ring 20. `It will-then rebound or be directed back into the spout I5 Where it wi11\be carried back into the rotor element I2 until it is reduced to the desired degree of neness. The unreduced particles that are not thus redirected back into the spout I 5, but which I0 escape around the sides thereof, will fall down into the drum I6, Where they will be picked up by the scoops or pockets 38 and carried up to a. point directly above the rotor element I2 and the spout I5 and dropped back into th spout I5, or 4.5 into the path of the agglomerate projected outwardly by the rotor I2 to be carried along therewith andfagainst the impact plate 23, from which they will be projected into the spout I5. As the particles of the agglomerate are thus reduced some will escape downwardly between the ring 63 upon the rotor'element I2 and the lip 6I upon the spout I5 and the remainderfwill fall down clear of the spout I5 and into the bottom4 of the rotatable drum I6. l v

'I'he agglomerate will preferably be fed to the mill in a wet condition and sufficient additional Water will be introduced with or independently of the agglomerate to provide for 'an overflow of water through a discharge opening 35 formed N' in one end of the drum I6. This Water will pick up the finer particles of the'agglomerate in the drum I6 by suspension and/or notation and thus cause them to be decanted or floated from the mill in a continuous manner. A discharge pipe 36 is shown for the purpose of carrying the overflow from the drum I6 to any desired point. As the drum I6 rotates, the scoops 33 carried thereby will agitate the water, wash the larger particles, and thus leave the finer particles in suspension 'I0 in the water 31.

From the above it will be seen that the larger particles of the agglomerate will be acted upon in a continuous manner until theyhave been reduced to the required degree of flneness. It will 7.

be also apparent'that, since the velocity of acentrifugally projected body is proportioned to its mass, the intensity of the impact feature of the mill may be varied by increasing or decreasing' the speed oi the centrifugal rotor I2. The coarse,- ness of the iinished material decanted from the drum I6 may be 'also controlled by varying the depth and/or therate of' flow of the water from the bottom of the drum i6.

In this mill the impact ring 2@ is shown as carriedby the drum ISand as rotating therewith. While this is apreferred arrangement it is to be understood f that the impact ring may be held stationary if so desired. However, when this ring is rptated, as shown, the wear upon theA inner surface thereof will be uniform throughout its circumference and as a result it will last considerably longer than if it is stationary.

J -The operationLof the mill illustrated in Figure 4 of the drawings is substantially similar Vto that described above, except that the centrifugally thrown agglomerate, instead of striking the steel impact ring 20, will strike a mass of agglomerate which will be held by centrifugal force in the outer centrifugal rotor 4. This difference in the construction of the two mills illustrated great- A rotor It and the outer rotor di will be so regu- 4Q' lated that the agglomerate fed tothe inner rotor will be thrown out near the upper edge thereof and contact the outer centrifugal rotor 4I over an areaimmediately above the chute 52 so that the major portion, if not all of the agglomerate thusL thrown, will be'directed back into the chute 52 where it will comingle with the agglomerate being fed from the hopper 5i.

As. shown, the scoops 59 are inclined insuch a direction that they will drop the larger particles, picked up thereby, Adirectly into the chute 52,

Figure 1 of the drawings. In this mill the decanting of the finely reduced agglomerate from 55 the drum 53 `wil1 be accomplished in a manner 'i similar-to that, described above. f

In the mills contemplated by this invention the action which takes place', in so far as the impact feature of -reduction is concerned, is somewhat simi r to that whichvtalres place in the well kno ,-Hatsell mill, wherein thepartlcles are pickedrupv by a rotating drum having a compara,- tively largexdiameteri and dropped by graviti7 upon an anvil disposed within the ring.. How- 35 ever, in the present disclosure the agglomerate is thrown, at a high velocity, by centrifugal force against an impact member and as a result the impactv is more intense than is the case in the Hatsell mill, wherein the agglomerate is merely dropped upon an anvil. If the mills are `to be used for the reduction of dry agglomerato, and a drum 61, such as is illustrated in Figure 6 of the drawings, is provided about the centrifugal rotor elements, the

ilnely `reduced agglomerate will sift out through g pulverizedagglomerate may be discharged from,

the mill asf a. thick muddy mass.

While I have, for the sake of clearness and in order to disclose the invention so that the same can be -readly"understood, described'and illustrated specific devices" and arrangements, I desire to have it understood that this/invention is not limited to the speciilc means disclosed, but may be embodied in other ways that will suggest themselves, in view of this broad disclosure, to persons skilled in the art. It is believed that this invention is broadly new and it is desired to claim it as such so that all such changes as come `Within the scope of the appended claims are-to lbe considered as part of this invention.

Having thus described my invention, what I' claim and' desire to secure by Letters Patent isl. In a pulverizing mill, the combination of a centrifugal bowl-like rotor adapted to rotate1 about a horizontalaxis, means for driving said.

rotor at high speed, aninwardly extending. lip

about the open end of said bowl-like rotor for retaining a layer of material therein against displacement by centrlfugal force when the bowllike rotor is in rotation, and means adjacent 'the openend of said rotor for feeding` material to be pulverized over said lip and into said rotor, the inward extension of the lip about-the operi end of said rotor being sufiicientvto retain a loro;

tective layer of the material being pulverized over the entire inner surface of said rotor.

2. In a pulverizingmill, the combination of a 1' bowl-like rotor adapted to receive and throw marather than in the path of the thrown Vagglomcrate, asis the case in the mill illustrated in' terial therefrom by centrifugal force, means for driving said rotor at high speed, an inwardly.` 

